A

B

C

D

E

The phenomenon in which, for certain reactions, product ratios change as the reaction progresses.

F

G

Geminal (gem-)

When two functional groups are bonded to the same carbon, they are said to be geminal.

H

I

J

K

L

M

Markovnikov's Rule

Markovnikov's Rule predicts the primary product of an addition reaction. It states that in an electrophilic addition reaction, hydrogen is added preferentially to the carbon already having the most hydrogens—that is, to the least substituted carbon. This rule holds for mechanisms in which the first reaction step is the addition of hydrogen and formation of a carbocation, and the second is the attack of that carbocation by a nucleophile. The carbocation produced in the first step will form on the more substituted carbon, since the positive charge is more stable there. This leaves the less substituted carbon for the hydrogen. Additions which do not follow Markovnikov's Rule are called Anti-Markovnikov Additions.

N

O

P

Q

R

S

T

U

V

Vicinal

When two functional groups are bonded to adjacent carbons, they are said to be vicinal. Usually applied to two of the same functional group.

W

X

Y

Z

Zaitsev's Rule

In an elimination reaction, hydrogen is removed from the carbon which already has the least hydrogen—that is, from the most substituted carbon. More precisely, in an elimination reaction the primary product is the most stable alkene. In general, more substituted alkenes are more stable.